1. Field of Invention
This invention relates to the dispensing of powders. More particularly, this invention relates to apparatus and methods for dispensing powders.
2. Description of Related Art
Dispensing systems are used to dispense powders from a container into a receiving vessel. The container is typically attachable to the receiving vessel via a gasket arrangement during the dispensing operation. A dispensing valve controls the discharge of the powder from the container during dispensing operations. In such dispensing systems, if the gasket arrangement does not fit correctly, or if the container and receiving vessel are not perfectly aligned, then the powder tends to leak into the dispensing facility. This leakage of the powder can occur during dispensing, or after dispensing has been completed and the container and receiving vessel have been separated from each other. Depending on its composition, the leaked powder may cause health and safety concerns for persons in the facility. In addition, the leaked powder material can create housekeeping problems and results in material waste.
Furthermore, in such known dispensing systems, even when the gasket arrangement works correctly and leakage of the powder is well contained during the dispensing operation, subsequent leakage still occurs. For example, when the container and receiving vessel are separated from each other, powder that has adhered to the dispensing valve can become entrained in the air or drop onto the floor of the facility, causing the above-mentioned problems.
Another problem encountered in known powder dispensing systems is achieving a controlled flow of the powder from the container to the receiving vessel. Fine powders tend to agglomerate due to interparticle friction and electrostatic interaction of the powder particles. Known dispensing systems have addressed this flow problem by including fluidizing devices. For example, vibrators and flexible inflatable liners have been installed in known dispensing systems to improve the fluidity of the powder, so as to enhance feed control. However, although these fluidizing devices may enhance the flow of the powder, they have at the same time created additional problems. For example, the inflatable liners require venting of the air, which increases the complexity of the dispensing system. Inflatable liners can als be a source of fibers, which can contaminate the powder material. Accordingly, such fluidizing devices have not been completely satisfactory in known dispensing systems.
U.S. Pat. No. 4,974,646 to Martin et al. and U.S. Pat. No. 5,727,607 to Ichikawa et al., the entire disclosures of which are incorporated herein by reference, disclose apparatus for feeding powders that utilize members formed of porous materials to promote powder flow.
Thus, there is a need for a dispensing system for dispensing powders that can overcome these and other problems of known dispensing systems.